The present invention relates generally to centrifugal pumps and, more particularly, to a centrifugal fuel pump mounted to an aircraft engine.
The fuel delivery system of an aircraft supplies fuel to aircraft engines and typically includes a boost pump mounted to the engine. The boost pump receives fuel from fuel tanks mounted on the aircraft and supplies fuel to the main frame pump mounted to the aircraft frame.
The boost pump impeller, imparting increased pressure and flow rate to the fuel, and the volute collector, guiding fuel from the impeller to the boost pump outlet, are among the principle contributors to boost pump performance. Fuel flowing through pumps has potential energy, generally characterized by static pressure, and kinetic energy, generally characterized by dynamic pressure. The sum of the static and dynamic pressures defines a total pressure of the fuel. Efficient pump impellers impart tangential velocity, and therefore dynamic pressure, to the fuel exiting the impeller with minimal input power. The volute collector reduces the velocity and thereby coverts dynamic pressure into static pressure, a process sometimes referred to as pressure recovery. The combination of impeller and volute collector geometry govern pump performance.
Fuel boost pumps are designed to provide an uninterrupted supply of fuel to the main frame pump within a particular pressure and flow rate envelope under all operating conditions encountered by the fuel delivery system during an aircraft flight. Under normal in-flight operating conditions, the fuel tank pressure decreases as altitude increases following the natural depression in the ambient atmospheric pressure, and the fuel temperature varies between −40° F. and 300° F. Under abnormal conditions, the main frame pump can fail or the boost pump can become partially obstructed. Under each set of conditions, the boost pump delivers 100% liquid fuel when a ratio of fuel vapor to liquid fuel (V/L) at the boost pump inlet is 0.45 or more. Furthermore, boost pumps are designed to deliver a maximum outlet pressure such that heat exchangers, filters, and other downstream components do not fail under the boost pump pressure. Maintaining the operational envelope and overall efficiency of the boost pump in view of all the operational conditions during an aircraft flight sometimes involves multiple pumps, each pump tailored for a subset of the operating conditions encountered during flight. However, multiple pumps increase the weight and complexity of the fuel delivery system.
Reducing the weight and complexity of fuel delivery systems while increasing component performance and efficiency continues to be a goal of designers and manufacturers. Therefore a need exists for a high-performance, efficient boost pump that can deliver fuel to the main frame pump within an operational envelope for all conditions during an aircraft flight.